Osteoporosis and its associated fractures represent an increasingly important health problem among older men. It is estimated that approximately one-third of all hip fractures occur in men. The lifetime risk of hip fracture in white men age > is about 6%, less than the lifetime risk of 18% in 50 year old white women. Recent data suggest that vertebral fractures are as common in men as in women. Osteoporosis is also an important contributor to disability in older men. Mortality after a hip fracture may actually be higher among men than women. In contrast to the vast amount of data that has accumulated on the etiology and prevention of osteoporosis in women, considerably less I s known about osteoporosis in older men. We propose to continue our Study of Osteoporotic Risk in Men (STORM), an observational study of the determinants of bone mineral density (BMD) in 523 men, ages 50-88. Men originally studied between 1991-1992 will be reconnected for a follow-up examination to be completed as part of this application in 1998- 1999 (after approximately 75 years of follow-up). Based on follow- u rates in our other studies, we expect that at least 75% of the cohort will return for a clinic visit. BMD at the proximal femur and lumbar spine will l be remeasured using dual-energy x-ray absorptiometry, and the annualized rate of change in BMD at these skeletal sites determined. 1.) Examine the pattern and determinants of one loss in older men to test several hypotheses 2). To test the hypothesis that allelic variation at the apolipoprotein E gene locus predicts BMD bone turnover and the rate of bone loss. 3). Describe the prevalence and risk factors for vertebral fractures in older men to test several hypotheses: The long-term objective of this project is to improve our understanding of the causes of age- related bone loss and the risk factors for vertebral fractures in men.